| Entrophication of water body is one of the most important problems in china.The basic reason of entrophication is the excessive nutrients in water,in which the main controlling factors are nitrogen and phosphorus.The eutrophication level of reservoir water is largely due to the release of nutrients and phosphorus from sediments, especially after the external pollution sources are controlled effectively.The exchange of nitrogen-phosphorus nutrients at the interface of sediment-water is affected by the characteristics of overlying water,microorganisms,temperature,disturbance and other various factors.And the mechanism and process is much more complex.So it is necessary to do further study about the inner pollution of sediment.The experiment study is about the sediment of Xi'an water source.Through the indoor static simulation of sediment-water interface environment,the effects of microbial on nitrogen release were studied,especially the effects on the conversion among the nitrogens in sediments.Through two series of comparison tests,the following conclusions were obtained.(1) At atmospheric temperature,the experiment was divided into aerobic and anaerobic stages.At the aerobic stage,nitrification was more obvious and the concentration of nitrate nitrogen was increased obviously.At the anaerobic stage, ammonia had a significant releasing trend and it is the main form of nitrogen release. Under anaerobic conditions,it occurred denitrification of nitrogen and anaerobic ammonia oxidation in the non-sterile devices by the role of micro-organisms,nitrogen will be released as gaseous form from water body.(2) At low-temperature condition,the release of ammonia was accompanied by organism release.As the main form of nitrogen release the release rates of ammonia under sterilized and non-sterilized conditions were 1.3574mg/m~2·d and 1.0122mg/m~2·d, respectively.Thus,the release in the non-sterilized device was more obvious.And the initial oxygen consumption rate in the device was 70mg/m~2·h and the average rate was lately up to 15mg/m~2·h.After 17days,the dissolved oxygen was down to 0mg/L,while the value in the sterilization device was about 2mg/L.The tests of organic matter and total nitrogen showed that TN in non-sterilized sediments was 1167.65μg/g and the content of organic matter was 3.30%.At the end of the experiment,TN was 968.76μg/g and the content of organic matter was 2.99%.TN in the sterilization device had little changes,TN was 1107.98μg/g,1079.57μg/g before and after experiment,while the content of organic matter was increased.(3) The measurement of nitrogen in sediment interstitial water showed that the contents of nitrate and nitrite were low.The content of them respectively was 0.312 mg/L,0.580 mg/L,accounted for 3.08%,5.74 of total nitrogen.Ammonia and organic nitrogen were the main components of TN in interstitial water,accounted for 60.64%, 30.54%of total nitrogen.The difference of concentrations between the interstitial and overlying water indicated that the concentration gradient could promote the nitrogen release from sediment,but it was not the deciding factor.(4) The measurements of nitrogen in sediments were divided into ion exchange form(IEF),carbonate-bound form(CF),Fe-Mn bound form(IMOF) and organic and sulfide form(OSF).The results showed that 39.66%nitrogen in sediments can be transformed,in which IEF-N,CF-N,IMOF-N and OSF-N contents were 63.64μg/g, 101.41μg/g,105.21μg/g,192.80μg/g,respectively.In ion exchange form 90%was ammonia-N.After the experiment IEF-N,CF-N,IMOF-N and OSF-N contents were 37.20μg/g,45.46μg/g,93.26μg/g and 89.32μg/g,respectively.And OSF-N,IEF-N and CF-N had great influences on nitrogen release from sediments.
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